ABSTRACT Chronic HBV infections (CHB) are a major global health concern. While multiple treatment options exist for CHB, they are rarely curative. Scientific focus is now shifting towards CHB cure research, but curative treatments have remained elusive due to persistence of covalently closed circular DNA (cccDNA) in infected hepatocytes despite anti-viral therapies, providing the template for further viral replications. CHB patients exhibit narrowly focused T cell responses and HBV immunotolerance, resulting in failure of conventional vaccination approaches. However, curative clinical results from bone marrow transplantations and T cell-based immunotherapeutic strategies in CHB animal models, indicate T cells can potentially control or clear CHB. T-cell redirecting bispecific Abs are the most potent type of therapeutic Abs to date, showing durable and high response rates in hard-to-treat cancers. HBV surface antigen (HBsAg)-specific T-BsAbs were successfully tested in animals, showing effective elimination of infected cells in vitro and in vivo. However, these T-BsAbs do not cross-react with primate T cells, limiting their testing viability, and/or include strong T cell activation and high cytokines production with significant toxicity. TeneoBio developed a one-of-a-kind platform based on a fully human heavy chain only Abs (UniAbs), a high throughput NGS-based bioinformatics pipeline (TeneoSeek), and proprietary UniAb-producing animals (UniRats). The fully human, heavy chain only structure of UniAbs facilitates multivalent binding for potent and specific kill of cells with low antigen densities, promotes stability (even at extreme temperature and pH conditions) and predicts a superior safety profile. Importantly, we have used it to develop a novel type of ?CD3 moiety that mediates selective cell kill with minimal cytokine secretion and preferential effector T cells activation, thus avoiding patient borne toxicity. In this program, TeneoBio scientists will join forces with expert HIV and HBV virologists and immunologists at Oregon Health & Science University to harness these innovations towards developing a best-in-class trivalent T-BsAbs with biparatopic targeting of HBsAg on infected cells together with a unique ?CD3 moiety that reacts with both human and rhesus macaque T cells with the goal of activating adjacent T cell and degrading the nuclear cccDNA reservoir. In Specific Aim #1 UniRats will be immunized with HBsAg (the universally effective Recombivax HB vaccine) to generate a high titer anti-HBV response. Then, UniRats? lymph nodes will undergo high throughput NGS identification of ~300 putative high specificity and affinity UniAbs leads against HBsAg. In Specific Aim #2, sequence families identified in SA1 will be cloned and expressed; characterized for manufacturability, specificity, and affinity in primary functional screens; then tested for binding to surface-expressed HBsAg on HBV-infected human and rhesus macaque primary hepatocytes. Phase II will focus on generating T-BsAbs comprised of rhesus macaque/human cross-reactive, low-agonist ?CD3 moiety and five different ?HBV moieties selected in Phase I, for in vitro and in vivo studies. Put together, these studies will allow us to file an IND application and to initiate Phase I clinical trials.